Submarine signaling



Jufiy 15 M24. 1,501,105

R. A. FESSENDEN SUBMARINE S I GNALI NG Filed March 23, 1918 577477TEMP/1; 9/1/5 Patented July 15, 1924.

BUBMABINE SIGNG.

Application filed March 28, 1918. Serial No. 224,288.

To all wiwm it may concern:

Be it known that I, REGINALD A. F ESSEN- DEN, of Brookline, in thecounty of Norfolk and State of Massachusetts, a citizen of the '5 UnitedStates, have invented new and use- Improvements in Submarine Signaling,of which the following is the specification.

My invention relates to the generation and j utilization of elasticimpulses and more particularly to submarine signaling, and still moreparticularly to the detectlon of submarines.

The figure forming a part of this specification, shows partlydiagrammatically, 16 means adapted for carrying out my 1n-' vention.

My invention has for its object the increased efliciency zation'ofelastic im ulses and in submarine 2o signaling and in t e detectionrines, and other similar bodies.

Referring to the figure, 11 is a tank containing fluid, for example afuel oil tank or a water tank, preferably extendin' the full as. widthof the vessel 23 and prefera 1y intermediate between the bow of thevessel and the stern of the vessel, as the separation from the bow tendsto reduce the water noise and the separation from the stern tends to 80reduce the machinery noises, and especially if there are othercompartmehts, such as'12.

and 13, inserted between the tank 11 and the bow of the vessel andbetween the tank 11 and the machinery compartment of the vessel, asthese compartments 12 and 13 act as sound screens.

An additional advantage of having the tank in this intermediate locationand also extending from one side to the other of the vessel, is that onaccount of the bending of the sound waves, signals can be sent and heardand submarines detected ahead or astern substantially'equally as well,or better than abeam.

The tank 11 need not be a single tank but may be divided up into a numer of compartments, for example by the horizontal bulkhead 14. Thishorizontal bulkhead l is preferably several feet below'the water line ofthe vessel and is preferably sound proof, as it has been found thatbythis construction water noises are very largely kept in the generationand utiliof submaaway from thereceiving apparatus, which lower-part of 1is preferably located in the the tank 11, i. e. between the horizontalbulkhead 14 and the'bilge ofthe vessel.

When it is desired to use the fuel oil from one portion of the tank 11,for example from the upper portion, this 011 may be pumped into a secondtank 15 and used from thence the upper portion of the tank 11 beingfilled with sea water. In this way the tank 11 may be kept full all thetime and the noise of the swashing around of oil minimized.

en it is desired totake in more oil, the sea water is pumped out .andthetanks steamed in'the usual way, the steam in this case removing the lasttraces of the salt Water, just-as in ordinary practice it is used toremove the last traces of oil. Ur, if desired, the upper portion of thetank may be left empty.

16 is a cross shaped sound screen and 17, 18, 19, 20 are signalingapparatus placed one in each angleof the cross shaped sound screen.

These signaling ap aratus are preferably such as are suitable f ing orcondenser transmitters and receivers of the type herein described. I

Apphcant has discovered that electric capacities or condensers are veryefficient transmitters and receivers of compressional waves in liquids.Such capacities maybe of the usualball or plate form, bat are preferablymade up of metallic films alternately connected toge separated by adielectric.

The dielectric is preferably elastic and homogeneous and may be made ofindia rubber, glass, mica, -or'paper saturated with paraffine or oil. Infact, any good insulatmg material may be used.

In the figure, 17 ai1d18 represent, diagrammatically, condensers "havinga solid dielectric .of mica or glass and. 19 and 20 represent condensershaving a dielectric composed of paper saturated with/oil or oil withoutpaper, and enclosed in boxes 21, 22 to prevent the fluid dielectric frommixin with the oil in the tank 11 Vhen an alternatin voltage isimpressed on these condensers, r exampleby'means er and or sending andreceivplates or j of the alternating current generator 25 and keys 26,27, the electrostatic attraction between the metallic plates or films ofthe condensers 19 and 20 compresses the dielectric between the platesand a compressional wave travels out, being transmitted from thecondensers to the fluid surrounding the condensers, which in the caseshown is the oil in the tank 11, and thence to the water surrounding thevessel.

A source of continuous current voltage, as shown in 24, ispreferablyplaced in series with the sourm of alternating current voltage toincrease the strength of the signals.

In this way compressional waves may be emitted from either or both ofthe condensers 19 and 20 and-may be transmitted out in the direction thequadrant of the sound screen 16 faces, in which the condenser is placed.

The frequency of the compressional waves emitted will depend upon thefrequency of the alternating voltage source 25. The compressional wavesare preferably either ordinary sound waves of a frequency of about 500to 1000, or for other work preferably anacysms, i. e. compressionalwaves above the limit of audibility. The use of a technical term toexpress the concept of dilatational waves in material media and of afrequency above thatof audibility has been felt for some time,.and anumber of terms have been prop The term anacysms is preferred, as it haspriority, having been used by applicant in a report to the U. S. Navy,Dec. 21st, 1912; and it is good Greek, having been used by Aristotle;while supersonics has been derided by classicalscholars as meaningsomething quite diiferent, i. e. something sounding above other noises,as a trumpetin battle. I have found that anacycms havin' a frequency ashigh as 40,000 are suitable, ut frequencies as high as 100,-

000 or even 200,000 per second may be used.

Receiving on a condenser submarine'signaling apparatus ma beaccomplished in a number of ways. or example, the, condensers 17 and 18may be charged by the source of continuous voltage 28 and connected tothe head phones 29, 30. Sound waves-originating from a source ahead ofthe vessel, on strikin the condensers 17 and 18 alter the capacity ofthe condensers and hence alter the charges on the condensers and. henceproduce an alternating current in the circuit ers and the head a soundin the head phones. If the sound source is located off the port bow of.the vessel the intensity of the sound waves received by the condenser 17will be greater than that received b the condenser 18 and hence thechange 0 capacity in the condenser 1'7 and the sound produced in thehead phone 29 wil1 be greater than that f 27 are signaling keys keptreceived by the condensers compounds, in the well known containing thecondens- "g phones and hence produce 4 ducing well known forms,

the condenser 18 and head phone 30. In this way it is possible to tellwith sufiicient accuracy for most purposes the direction of the soundsource, and if it is desire to know the direction exactly the vessel maybe caused to turn to port until the sound comes in with equal strengthon the-head phones 29 and 30 and when this is the case the vessel willbe pointing directly to the source of sound.

In place of receiving in the manner above described, applicamsheterodyne method may be used and this is especially useful whenanacysms are used-for signaling.

A suitable arrangement is shown in connection with the condensers 19 and20, where 25 is a ource of alternating current having 40,000 a second;26 and a frequency of about closed for receiving; 24, 24 are sources ofD. C. volta e, which are preferably used as givin lou er signals butwhich may be omitte if deslred. 31, 32 are. primaries of a transformerarranged to act oppos'tely to each other on the secondary 33, wherebythe direction of the sound is more easily determined by noticing whichis the stronger.

When no compressional waves are being 19 and 20, the currents. flowinginto the condensers create, by means of the primaries 31 and 32, equaland opposite voltages on the secondary 33 and hence do. not cause anycurrent to flow throughthe circuit containing the secondary 33 and thestatic telephone 34.

35 is a source of alternating current voltage of approximately afrequency of 39,000 a second and this is connected to the terminals ofthe static telephone 34 and to the secondary 33, as shown, but does notproduce any-sound in the. static telephone 34 so long as nocompressional waves are being received by the condenser 19 and 20,because this frequency of 39,000 is above audibility.

But on compressional wavesarriving from the port quarter and strikingthe condenser 19, the capacity of the condenser 19 is caused to vary andthe voltages impressed by the primaries 31, 32 no longer balance eachother and a current of the frequency generated by the generator 25,flows through the circuit 33, 34 and this method, with the current.generated bythe enerator 35, i. e. 39,000 per second, so as frequency.of 1,000 per second in the static telephone 34, thus proan audiblesignal.

-The. heterodyne .me'hod-of receivin in the form above described or inany 0 the is especially well adapted for receiving, because iteliminates disturb ing noises, especially theseare ofcomparatively lowfrequency.

i. e. 40,000 per second,

heterodyne water noises, since It is preferred when frequencies above40,000 are used to have the oscillator tube described in Letters PatentNo. 1,167,366 shortened, or else to work on a frequency that is amultiple of the quotient of the mitter, the apparatus will be extremelyin- .eflicient unless the dielectric is of the same order of density asthe liquid in which the condenser is immersed. For though air is a goodinsulator, if the condenser 19 is constructed with an air dielectric theefliciency as a receiver or transmitter will be only of the order of oneper cent or less than if the dielectric has a den- I sity of the orderof unity.

For a similar reason it is advisable that the elasticity of thedielectric should be of the same order as that of the liquid in whichthe condenser is immersed.

When detecting submarines or similar bodies by echoes, the second highfrequency generator 35 is not necessary as the frequency. of theenerator 25 ma caused to vary regular y between the limits of say 35,000to 40,000, and hence signals sent out when the frequency is say 36,000w1ll be received back after reflection from the echo producing body onthe condenser receivers at the instant when the generator 25 isgenerating a frequenc of say 38,000, and hence beats will be p ucedhaving a frequency of 2,000 per second.

In this way the distance of the echo producing. body may be determined,by the number of beats produced; since the greater the distance apartthe greater the di erence in frequency of reflected and generatedoscillations.

In ex lanation of the increased efiiciency obtain the condenser platesconstituted of substances having the same order of density,

and also preferabl of elasticity, as the flmd in which, the con ensersare immersed, for examplesea water, the complete theory has not beenworked out, but it is probably due to the fact that when this is thecase, and especially when the elasticity and density have such valuesthat there is no difference in phase angle on passing from the fluid tothe condenser, the compressional waves are transmitted completely andproduce their full effect in varying the capacity of the condenser.While on the other hand, if the densit of the dielectric is of adifferent order 0 magnitude from that of the oil or sea water thecompressional waves are only partly transmitted, being reflected at eachayer'of the-condenser and on nenetratexample,

-'by having the dielectric between ing a small distance and alsb thephase ofv the compressional wave ma be quite different in differentparts of til that one part may be in compression while another part isin expansion whereby these two parts of the condenser will neutralizeteach others effect in producing an indica- From examination of thefollowing list of materials and densities,

Metals 0.53 to 22.4 Rll'bbel 1.2 Glass -l -3.0 Mica 3.0 Paraflined paper1.5 Sea water 1.03 Paraflin oil 0.9 Air 0.0013

it will be seen that the densities of the ma terials on the left, whichinclude all the standard non-gaseous dielectrics, and the metals whichmight be used for the conducting sheets of the condensers, are of anen-. tirely diflerent order of magnitude from the density on the right,i. e. that of air.

Consequently any standard commercial condenser made of the materials ofthe left hand column and used-while immersed in sea water or oilwill'bea condenser which has its dielectric and metallic armatnres ofthe same order of density as the medium in which it is operating. Whileif it has an air or gaseous dielectric, or is used in air or a gas, itwill not.

Heretofore condenser signal apparatus for producing and receiving soundshas always been of the latter class, i. c. has either had' a dielectricof air or gas, or has been used in a aseous medium. It hasconsequentlyhat? an extremely low efficiency, for reasons pointed outabove in the specification.

Applicants discovery and invention is that condensers of the firstclass, i. e. con-' structed of materials such, as those in the i lefthand column, and most of which are standard commercial articles, may bemade very highly efficient producers and receiv-.

of magnitude as regards density as the con densers .the'mselves. Inpractice the increase pf efficiency -has 'been experimentally found tobe in some cases more than 100 times, and to com-pare favourably withthe hitherto generally used microphones.

What I claim is 1. In the art of' submarine signaling, means forproducing and for detecting compressional waves in water, comprising acondenser having its dielectric and armatures of materials having theirdensities of e condenser so the same order of magnitude as Water; and

said condenser being-in operative relation to said water; 2. In the artof submarine signaling,

5 means adapted for the produetionandthe reception of compressionalwaves in ater, compr sing a condenser having its dlelecarmatures ofmetal; said condenser 10- immersed in and in operative relation to sew'ater.

RE INALD A, FEssENDE-N.

